The optical properties of in polycrystalline(ceramic), and nanocrystalline forms of cubic (bixbyite) yttrium oxide are modeled based on the absorption spectra obtained between 400 and 1700 nm and the fluorescence spectra observed between 1500 and 1670 nm. Both spectra were obtained at 8 K. The observed crystal-field splitting and the measured intensities of transitions between Stark levels of the multiplet manifolds of in both the and sites of are analyzed in terms of established models. The inversion symmetry of sites limits the observed electronic transitions to magnetic dipole transitions between the and manifolds. There is no spectroscopic evidence for transitions involving other multiplet manifolds of ions in sites. For ions in sites, forced electric dipole transitions are allowed between the Stark levels associated with each manifold. With few exceptions, the crystal-field splitting and the intensities of the transitions between Stark levels are comparable between the nanocrystalline,polycrystalline, and the flame fusion grown crystals of cubic yttrium oxide containing trivalent erbium.

Analyses of the optical absorption and emission intensities are performed on ionsdoped into yttrium orthoaluminate to assess this material as a laser source. The Judd–Ofelt model is applied to the room temperature absorption intensities of in to obtain the phenomenological intensity parameters: , , and . The intensity parameters are used to determine the radiative decay rates and branching ratios of the transitions from the upper multiplet manifolds to the corresponding lower-lying multiplet manifolds of in . Using the radiative decay rates, radiative lifetimes of 13 excited states have been determined. The room temperature fluorescence lifetime of the transition is measured to be 0.43 ms. Values of emission cross section and peak emission cross section have been obtained for the and intermanifold transitions. The detailed structure observed in the manifold-to-manifold transitions allows us to identify the Stark splitting of the individual manifolds.

Resonance frequency of freestanding, square-shaped thick metal screens have been studied here in the wavelength range of infrared (IR) to mm (20 to 0.2 THz). It was found that their peak transmission has a linear relationship to the screen’s pitch. An experimental spectral feature, unaccounted for in typical simulations with plane parallel incident beams, was observed in the transmittance envelope for measurements in focused beams. In the past, this spectral feature was assigned to Wood’s anomaly. Yet, unlike the latter, the observed spectral feature appears here in the long wavelength regime as well. We investigated this phenomenon for a large frequency range and assigned the spectral feature to the formation of a photonic band gap at oblique incidence. Many IR Fourier transform spectrometers use a noncollimated incident beam and such spectral features will appear whenever the local state of polarization includes components which are parallel to the plane of incidence.

The defect structures in superlattices(SLs) on substrates grown by molecular-beam epitaxy have been investigated using (scanning) transmission electron microscopy and electron energy loss spectroscopy. Straight Hg-rich defects perpendicular to the SLs have been observed near the substrate while Frank dislocation loops (FDLs) are seen far from the substrate. The Hg-rich defects exhibit only a compositional variation with no significant atomic shift, and can be considered to be a remnant of a FDL which has climbed by thermal diffusion during the growth.

We report the generation of extreme ultraviolet radiation with high photon flux , high spatial coherence (up to 0.95), and good spatial beam profile by high-order harmonic generation in various noble gases (argon, neon, and helium) in a gas cell. The photon flux was determined using an extreme ultraviolet spectrometer equipped with a charge-coupled device camera and the spatial coherence was determined from Young double-slit interference fringes. The high-order harmonic emission is confined to just a few orders because of the small phase mismatch in the cut-off region that allows macroscopic phase matching to be satisfied for just a few harmonics in this region. The efficiency and spatial beam profile are studied as a function of gas pressure and geometrical configuration.

The driving force for formation of a surface relief grating on an azobenzene-containing polymer is theoretically analyzed and experimentally confirmed by polarization analyses. We formulate the driving force based on the Coulomb interaction between an optical electric field and its induced polarization charges. The formula derived includes not only the optically induced gradient force but also the force due to the spatial modulation of the refractive index. The latter stems from the reorientation of the azobenzene molecules in the polymer through the cyclic trans-cis photoisomerization caused by the laser used to construct the interference pattern.

The lateral composition modulation that is present in InGaAsquantum wells(QWs) produces an asymmetry in the plane of the QW with two regions where transition to the heavy hole (HH) can occur. Polarization resolved photoluminescence shows that transitions between the conduction band to HH subbands in both the In-rich and Ga-rich regions produce anisotropic features. Also, changing the relative separation of the light hole and HH subbands has little impact on the separation of the anisotropic features of the photoluminescence curves.

This paper describes the spectral broadening of cholesteric liquid crystalfilm prepared from a blend comprising a cross-linkable liquid crystal polymer and a non-cross-linkable low-molecular-weight liquid crystal. The spectral broadening arises from the formation of gradient pitch across the film thickness. It is shown that both phase-separation and in situ swelling during photopolymerization are important mechanisms for the resulting film structure. The surface anchoring is important to achieve high wavelength- and polarization-selective reflectance.

We report optical transmission and reflection spectralmeasurements in the visible and near infrared on a one-dimensional transmission grating having a metal film deposited on deep rectangular subwavelength grooves etched in quartz.Measurements are made for both classical and conical diffraction geometry by varying the azimuthal angles between the plane of incidence and the grating vector. Strong differences for transverse electric (TE) and transverse magnetic (TM) polarized light are seen. We find conditions under which the transmission is negligible irrespective of light polarization and angle of incidence. The transmission spectra show deep dips corresponding to excitation of surface plasmons by TM polarized light when , by both TE and TM light when and by TE light for . We also examine the reciprocity behavior of the optical properties for incidence from the metal and substrate sides and dependence on light polarization.

We report on nonlinear upconversion photoluminescence(PL) of CdS nanocrystals (NCs) embedded in a polymeric film. The CdS NCs of 2 nm radius are synthesized by an ion exchange method and highly concentrated in the two layers near the surfaces of a freestanding Nafion film. We observed the differences between the two-photon and one-photon excited PL emissions. The two-photon absorption cross section and quantum yield of CdS NCs were measured with femtosecond laser pulses at 800 nm excitation. The origin of PL, optical nonlinearity, and the figure of merit for optical switching have been discussed.